Upregulation Of Cyclooxygenase-2 mRNA Research Articles

Lovastatin lactone elicits human lung cancer cell apoptosis via a COX-2/PPARγ-dependent pathway.

Statins (3-hydroxy-3-methylglutaryl coenzyme A [HMG-CoA] reductase inhibitors) are well-established agents to treat hyperlipidemic states. Experimental and epidemiological evidence further implies an anticancer effect of these substances. This study investigates the mechanism underlying human lung cancer cell death by lovastatin and the role of the prostaglandin (PG)-synthesizing enzyme cyclooxygenase-2 (COX-2) in this process. In A549 and H358 lung carcinoma cells the lipophilic prodrug lovastatin lactone led to a concentration-dependent decrease of viability and induction of DNA fragmentation, whereas its HMG-CoA-inhibitory, ring-open acid form was inactive in this respect. Apoptotic cell death by lovastatin was accompanied by high intracellular levels of the lactone form, by upregulation of COX-2 mRNA and protein, as well as by increased formation of peroxisome proliferator-activated receptor γ (PPARγ)-activating PGD2 and 15-deoxy-Δ12,14-PGJ2. Cells were significantly less sensitive to lovastatin-induced apoptotic cell death, when the expression or activity of COX-2 was suppressed by siRNA or by the COX-2 inhibitor NS-398. Apoptosis by lovastatin was likewise reversed by the PPARγ antagonist GW9662. Fluorescence microscopy analyses revealed a lovastatin-induced cytosol-to-nucleus translocation of PPARγ that was inhibited by NS-398. Collectively, this study demonstrates COX-2 induction and subsequent COX-2-dependent activation of PPARγ as a hitherto unknown mechanism by which lovastatin lactone induces human lung cancer cell death.

Ciglitazone inhibits cigarette smoke solution-induced inflammatory responses in human middle ear epithelial cells

ObjectivePeroxisome proliferator activated receptor-γ (PPAR-γ), a member of the nuclear hormone receptor superfamily, plays an important role in the regulation of mucosal inflammation. The aim of this study was to investigate the anti-inflammatory effect of a PPAR-γ agonist, ciglitazone, on cigarette smoke solution (CSS)-induced inflammation in human middle ear epithelial cell lines (HMEECs). DesignHMEECs with or without ciglitazone pre-treatment were exposed to CSS in order to induce the inflammatory response. The suppressive effect of inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α) and cyclooxygenase-2(COX-2), were evaluated using real-time polymerase chain reaction and Western blotting. ResultsStimulation with CSS at 40μg/ml for 6h resulted in a 4.1-fold increase in the expression of TNF-α mRNA in the HMEECs. CSS-induced up-regulation of TNF-α mRNA was decreased by more than 2.8-fold in cells pre-treated with ciglitazone. The up-regulation of COX-2 mRNA and increased COX-2 protein expression induced by CSS were also inhibited by more than 3.7-fold with ciglitazone pre-treatment. ConclusionsThese findings suggest that the inflammatory response induced by CSS could be inhibited by ciglitazone, a PPAR-γ agonist, in HMEECs. As such, PPAR-γ agonists may have therapeutic potential for the treatment of otitis media.

Signaling pathway involved in cyclooxygenase-2 up-regulation by hepatocyte growth factor in endometrial cancer cells

Hepatocyte growth factor (HGF) is up-regulated in tissue repair and has been implicated in playing a role in this process through its anti-apoptotic and proliferative activities. Cyclooxygenase-2 (COX-2) is an inducible enzyme in the biosynthetic pathway of prostaglandins, and its activation has been shown to play an important role in cell growth. We previously reported that HGF significantly inhibited anoikis, possibly through the up-regulation of COX-2 expression in the endometrial RL95-2 cancer cell line. Here, we report that i) treatment of RL95-2 cells with HGF resulted in phosphorylation of the HGF receptor c-Met, activation of Akt and IκB, translocation of NF-κB into the nucleus, and up-regulation of COX-2 mRNA; ii) the IκB-α phosphorylation inhibitor BAY11-7082 and the selective COX-2 inhibitor CAY10452 blocked HGF-mediated anoikis resistance in RL95-2 cells; and iii) HGF induced migration and invasion in RL95-2 cells, while the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 and CAY10452 blocked these effects of HGF stimulation. Our data suggest that HGF possesses chemotactic ability, has anti-apoptosis action, and induces cellular infiltration via the PI3K/Akt pathway; it also triggers NF-κB activation and up-regulates COX-2 gene expression in endometrial cancer cells.

γ‐Tocotrienol Reduces Squalene Hydroperoxide‐Induced Inflammatory Responses in HaCaT Keratinocytes

Squalene hydroperoxide (SQ-OOH), the primary peroxidation product of squalene (SQ), accumulates at the surface of sunlight-exposed human skin. There are however only a few studies on the pathogenic actions (i.e., inflammatory stimuli) of SQ-OOH. Here, we evaluated whether SQ-OOH induced inflammatory responses in immortalized human keratinocytes (HaCaT). We found that SQ-OOH caused an increase in the expression of inflammatory genes such as the interleukins as well as cyclooxygenase-2 (COX-2). In concordance with the upregulation of COX-2 mRNA, SQ-OOH enhanced reactive oxygen species generation, nuclear factor kappa B activation, COX-2 protein expression, and prostaglandin E2 production. Therefore, the pro-inflammatory effects of SQ-OOH may be mediated in part via COX-2. On the other hand, gamma-tocotrienol (gamma-T3, an unsaturated form of vitamin E) was found to ameliorate the SQ-OOH actions. These results suggest that SQ-OOH induces inflammatory responses in HaCaT, implying that SQ-OOH plays an important role in inflammatory skin disorders. As a preventive strategy, inflammation could be reduced via the use of gamma-T3.

Hepatocyte growth factor regulates cyclooxygenase-2 expression via β-catenin, Akt, and p42/p44 MAPK in human bronchial epithelial cells

Hepatocyte growth factor (HGF) is upregulated in response to lung injury and has been implicated in tissue repair through its antiapoptotic and proliferative activities. Cyclooxygenase-2 (COX-2) is an inducible enzyme in the biosynthetic pathway of prostaglandins, and its activation has been shown to play a role in cell growth. Here, we report that HGF induces gene transcription of COX-2 in human bronchial epithelial cells (HBEpC). Treatment of HBEpC with HGF resulted in phosphorylation of the HGF receptor (c-Met), activation of Akt, and upregulation of COX-2 mRNA. Adenovirus-mediated gene transfer of a dominant negative (DN) Akt mutant revealed that HGF increased COX-2 mRNA in an Akt-dependent manner. COX-2 promoter analysis in luciferase reporter constructs showed that HGF regulation required the beta-catenin-responsive T cell factor-4 binding element (TBE). The HGF activation of the COX-2 gene transcription was blocked by DN mutant of beta-catenin or by inhibitors that blocked activation of Akt. Inhibition of p42/p44 MAPK pathway blocked HGF-mediated activation of beta-catenin gene transcription but not Akt activation, suggesting that p42/p44 MAPK acts in a parallel mechanism for beta-catenin activation. We also found that inhibition of COX-2 with NS-398 blocked HGF-induced growth in HBEpC. Together, the results show that the HGF increases COX-2 gene expression via an Akt-, MAPK-, and beta-catenin-dependent pathway in HBEpC.

2,2′,4,4′-Tetrachlorobiphenyl upregulates cyclooxygenase-2 in HL-60 cells via p38 mitogen-activated protein kinase and NF-κB

Polychlorinated biphenyls (PCBs) are ubiquitous, persistent environmental contaminants that affect a number of cellular systems, including neutrophils. Among the effects caused by the noncoplanar PCB 2,2′,4,4′-tetrachlorobiphenyl (2244-TCB) in granulocytic HL-60 cells are increases in superoxide anion production, activation of phospholipase A 2 with subsequent release of arachidonic acid (AA) and upregulation of the inflammatory gene cyclooxygenase-2 (COX-2). The objective of this study was to determine the signal transduction pathways involved in the upregulation of COX-2 by 2244-TCB. Treatment of HL-60 cells with 2244-TCB led to increased expression of COX-2 mRNA. This increase was prevented by the transcriptional inhibitor actinomycin D in cells pretreated with 2244-TCB for 10 min. The increase in COX-2 mRNA was associated with release of 3H-AA, phosphorylation of p38 and extracellular signal-regulated kinase (ERK) mitogen-activated protein (MAP) kinases, increased levels of nuclear NF-κB and increased superoxide anion production. Bromoenol lactone, an inhibitor of the calcium-independent phospholipase A 2, reduced 3H-AA release but had no effect on COX-2 mRNA, protein or activity. Pretreatment with SB-202190 or SB-203580, inhibitors of the p38 MAP kinase pathway, prevented the 2244-TCB-mediated induction of COX-2 and phosphorylation of p38 and ERK MAP kinases. These inhibitors did not alter 3H-AA release. Treatment with PD 98059 or U 0126, inhibitors of the MAP/ERK (MEK) pathway, prevented the 2244-TCB-mediated activation of ERK but had no effect on COX-2 induction or p38 phosphorylation. 2244-TCB treatment did not affect c-Jun N-terminal kinase (JNK) phosphorylation. 2244-TCB exposure increased the amount of nuclear NF-κB. This increase was prevented by pretreatment with p38 MAP kinase inhibitors, but not by pretreatment with MEK inhibitors. Pretreatment with inhibitors of NF-κB prevented the 2244-TCB-mediated induction of COX-2 mRNA. 2244-TCB-mediated increases in superoxide anion were prevented by the NADPH oxidase inhibitor apocynin or the free radical scavenger 4-hydroxy TEMPO, but neither of these inhibitors affected the 2244-TCB-induced changes in COX-2 mRNA levels or 3H-AA release. Taken together these data suggest that p38 MAP kinase-dependent activation of NF-κB is critical for the 2244-TCB-mediated upregulation of COX-2 mRNA.

Upregulation of matrix metalloproteinase (MMP)‐1 and its activator MMP‐3 of human osteoblast by uniaxial cyclic stimulation

Proper mechanical loading is essential for bone remodeling and maintenance of human skeletal system. Matrix metalloproteinases (MMPs) are secreted by mesenchymal stromal lining cells and osteoblasts to prepare the initiation sites for osteoclastic bone resorption at the beginning of the remodeling cycle. However, only a few studies have addressed the effect of mechanical stress on MMPs and their endogenous tissue inhibitors of matrix metalloproteinases (TIMPs) in osteoblasts. In this study, the response of human osteoblasts to uniaxial cyclic stretching was investigated to clarify this more in detail. Stretching affected the orientation of the osteoblasts, and quantitative reverse transcription-polymerase chain reaction revealed coordinated upregulation of MMP-1 and its activator MMP-3 mRNA by cyclic 5% stretching at 3 h (p < 0.01). Upregulation of cyclooxygenase-2 mRNA was also found in response to cyclic 1 and 5% stretchings at 1, 3, and 6 h (p < 0.01). No changes were found in MMP-2, TIMP-1, and -2. The mRNA expression of MMP-9 was low and MMP-13 was not detected. This study suggests that MMP-1 and -3, enhanced by uniaxial cyclic mechanical stimulation of osteoblasts, are candidate key enzymes in the processing of collagen on bone surface, which might be necessary to allow osteoclastic recruitment leading to bone resorption. The strain might also play a role in cleaning of demineralized bone surface during the reversal phase, before bone formation starts.

Heparanase Is Involved in Angiogenesis in Esophageal Cancer through Induction of Cyclooxygenase-2

Both heparanase and cyclooxygenase-2 (COX-2) are thought to play critical roles for tumor malignancy, including angiogenesis, although it is unknown about their relationship with each other in cancer progression. We hypothesized that they may link to each other on tumor angiogenesis. The expressions of heparanase and COX-2 in 77 primary human esophageal cancer tissues were assessed by immunohistochemistry to do statistical analysis for the correlation between their clinicopathologic features, microvessel density, and survival of those clinical cases. Human esophageal cancer cells were transduced with heparanase cDNA and used for reverse transcription-PCR and Western blot to determine the expression of heparanase and COX-2. COX-2 promoter vector and its deletion/mutation constructs were also used along with transduction of heparanase cDNA for luciferase assay. Heparanase and COX-2 protein expression exhibited a similar pattern in esophageal tumor tissues, and their expression correlated with tumor malignancy and poor survival. Their expression also revealed a significant correlation with high intratumoral microvessel density. Up-regulation of COX-2 mRNA and protein was observed in esophageal cancer cells transfected with heparanase cDNA. COX-2 promoter was activated after heparanase cDNA was transduced and the deletion/mutation of three transcription factor (cyclic AMP response element, nuclear factor-kappaB, and nuclear factor-interleukin-6) binding elements in COX-2 promoter strongly suppressed its activity. Our results suggest that heparanase may play a novel role for COX-2-mediated tumor angiogenesis.

Up-regulation of cyclooxygenase-2 mRNA in the rat spinal cord following peripheral inflammation

Prostaglandins (PG) have been described as mediators in spinal nociceptive processing after peripheral inflammation. Enzymes essential for PG biosynthesis, cyclooxygenase isozymes COX-1 and COX-2, have not yet been investigated in the spinal cord. In two studies on rats with adjuvant-induced peripheral inflammation levels of mRNA expression of both COX isoforms were analyzed in the lumbar section of the spinal cord using reverse transcription-polymerase chain reaction (RT-PCR) technique. We could show that mRNA of both COX isoforms is expressed constitutively in the spinal cord with COX-2 as the predominant isoform. Six hours after induction of peripheral inflammation, levels of COX-2 mRNA expression were raised significantly in respect to untreated control rats and returned to baseline within 3 days after induction of inflammation. COX-2 might therefore be regarded as the COX isozyme responsible for spinal PG release in nociceptive processing under a peripheral inflammatory stimulus.